The Telegraph has learnt that energy providers cannot force meter readers to
use passwords or stop visiting at unearthly hours, upsetting some elderly
customers.

Maureen Waters has suffered from diabetes for 40 years. The 74-year-old is dependent on insulin to go about her daily life – and on rising each morning her husband, Fred, tends to her needs.

So when gas meter readers began calling at their home in Havant, Hampshire, at the crack of dawn, it was a major inconvenience for the elderly couple.

Despite his best efforts Mr Waters, 76, was unable to stop these nuisance knocks, with meter readers, purportedly working for his energy provider E.On, hassling him every few months at around 8am.

The Waters' frustrations are yet another example of how bungling energy firms have allowed customer service to slip to unacceptable levels.

Energy regulator Ofgem says bungled meter readings and inaccurate bills are responsible for 50pc of the complaints about power companies. Customers are frequently sent astronomical bills they do not deserve. In addition, some companies increase estimated bills in the winter months to account for increased usage, The Telegraph has learnt. This is against best practice and can lead to wild swings in direct debit payments, which must then be corrected by meter readers.

Calling an energy firm to complain is also expensive. Research by consumer group Which? found that npower's customers service line leaves callers on hold for an average of 17 minutes. By contrast, smaller provider EBIco answers in just 21 seconds.

Mr Waters, a retired civil engineering consultant, had tried to combat these inefficiencies by providing E.On with energy readings on the 25th of every month since December 2008.

Meter readers still called every three months – and always at reasonable daytime hours. But this year the pattern changed, to 8am on average.

Mr Waters tried giving E.On instructions not to call before 9am, and at the beginning of August he also asked for meter readers to use a password. Both conditions were agreed by the company.

But on August 27, a meter reader hammered at the door at 8.20am. When challenged, the man confirmed that he had not noticed an instruction on his hand-held device that advised him not to call before 9am.

Mr Waters was understandably furious that his instructions fell on deaf ears. He investigated and discovered that, like other energy firms, E.On employed a third-party contractor to read meters in some areas. This was G4S, the firm responsible for the London Olympics security fiasco.

An email sent to Mr Waters by E.On, seen by The Telegraph, appears to show serious flaws in the system.

It said: "We do have the option to put a password in the meter location part of your account, but I don't think the meter readers would necessarily look at this."

The issue now appears to be resolved. On October 1, Mr Waters received a letter apologising for the inconvenience. It read: "We have a responsibility to read your meters every 18 months for accurate meter readings and ensure the meters are working correctly and safely. In some regions we use third parties to read meters, in this instance G4S.

"[We have] arranged for meter readers to only visit after 9am and to also quote the agreed password when they visit."

Most major providers told The Telegraph that they used G4S to read meters, and admitted it could be difficult to stop readings being taken at inconvenient times.

The good news for those suffering at the hands of meter readers – whether it is inconvenience or bungled bills – is that so-called "smart meters" are being installed across the country. These devices are expected to be rolled out nationally from the autumn of 2015. They will provide live data to the energy firm, negating the need for physical visits to properties.